一 分欄控制器 UITabBarController
分欄控制器和導航控制器都是用來管理視圖控制器的

導航控制器是用來管理視圖控制器之間的導航，視圖控制器之間的層遞關系，一級-》二級-》三級。。

分欄控制器是管理固定的幾個視圖控制器，子視圖控制器之間是并列關系（平級關系），可以任意切換顯示；
分欄控制器可以管理導航控制器  ；
導航控制器不能管理分欄控制器；
【Demo】-【1-UITabBarController】
設計4個導航控制器，用分欄控制器管理

• (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions {

  self.window = [[UIWindow alloc] initWithFrame:[[UIScreen mainScreen] bounds]];
  self.window.backgroundColor = [UIColor whiteColor];
  [self.window makeKeyAndVisible];

  ViewController1 *vc1 = [[ViewController1 alloc] init];
  // vc1.title = @"主頁";
  // vc1.tabBarItem.image = [UIImage imageNamed:@"tab_0"];
  UITabBarItem *item1 = [[UITabBarItem alloc] initWithTitle:@"主頁" image:[UIImage imageNamed:@"tab_0"] tag:100];
  vc1.tabBarItem = item1;

  UINavigationController *nvc1 = [[UINavigationController alloc] initWithRootViewController:vc1];

ViewController2 *vc2 = [[ViewController2 alloc] init];

// vc2.title = @"頁面二";
// vc2.tabBarItem.image = [UIImage imageNamed:@"tab_1"];
UITabBarItem *item2 = [[UITabBarItem alloc] initWithTitle:@"頁面二" image:[UIImage imageNamed:@"tab_1"] selectedImage:[UIImage imageNamed:@"tab_2"]];
vc2.tabBarItem = item2;

UINavigationController *nvc2 = [[UINavigationController alloc] initWithRootViewController:vc2];


ViewController3 *vc3 = [[ViewController3 alloc] init];

// vc3.title = @"頁面三";
// vc3.tabBarItem.image = [UIImage imageNamed:@"tab_2"];
UITabBarItem *item3 = [[UITabBarItem alloc] initWithTabBarSystemItem:UITabBarSystemItemDownloads tag:101];
vc3.tabBarItem = item3;

UINavigationController *nvc3 = [[UINavigationController alloc] initWithRootViewController:vc3];



ViewController4 *vc4 = [[ViewController4 alloc] init];
vc4.title = @"頁面四";
UINavigationController *nvc4 = [[UINavigationController alloc] initWithRootViewController:vc4];
vc4.tabBarItem.image = [UIImage imageNamed:@"tab_3"];




//*************** 創建分欄控制器對象 *************//
UITabBarController *tabVC = [[UITabBarController alloc] init];
//把4個導航控制器對象給tabVC管理
tabVC.viewControllers = @[nvc1,nvc2,nvc3,nvc4];
//設置修飾圖片
tabVC.tabBar.selectionIndicatorImage = [UIImage imageNamed:@"tab_s"];
//設置tabBar上內容的渲染顏色
tabVC.tabBar.tintColor = [UIColor redColor];

//把tabBar設置為窗口的跟視圖控制器
tabVC.tabBar.barStyle = UIBarStyleBlack;
//設置是否透明
tabVC.tabBar.translucent = NO;
//根據設定的值來開啟初始界面
NSUserDefaults *defaults = [NSUserDefaults standardUserDefaults];
NSString *str = [defaults objectForKey:@"下標"];
int index = str.intValue;
tabVC.selectedIndex = index;

tabVC.delegate = self;
//把tabVC設置為窗口的根視圖控制器
self.window.rootViewController = tabVC;

return YES;

}

二 NSUserDefaults
數據本地存儲的方式：
1.plist文件
2.歸檔（存儲自定義的對象，對象要遵守NSCoding協議）
3.文件管理NSFileHandle，NSFileManager
4.NSUserDefaults 單例類
把內存中的數據存儲到本地，適合于存儲一些小型數據，比如：用戶名，密碼的保存；播放記錄，收藏記錄；
5.數據庫（存儲相比較大一些的數據）

pragma mark -UITabBarControllerDelegate

//當點擊tabBarItem的時候，會響應該方法
-(void)tabBarController:(UITabBarController *)tabBarController didSelectViewController:(UIViewController *)viewController{

NSLog(@"%ld",tabBarController.selectedIndex);
int index = (int)tabBarController.selectedIndex;
NSString *str = [NSString stringWithFormat:@"%d",index];

NSUserDefaults *defaults = [NSUserDefaults standardUserDefaults];
[defaults setObject:str  forKey:@"下標"];
[defaults synchronize];

}

三 如何自定義UITabBar 【開發中最常用】

步驟：
1.隱藏系統自帶的tabBar；
2.根據需求自己添加背景視圖（frame設置在tabBar的位置）；
3.根據項目有需求添加多個按鈕/label/UIView......，實現界面的切換
見【Demo】-【2-CustomTabBar】

• (void)viewDidLoad {
  [super viewDidLoad];

  NSMutableArray *mArr = [NSMutableArray array];
  for (int i=0; i<4; i++) {
  //循環拿到類名所對應的字符串
  NSString *className = [NSString stringWithFormat:@"ViewController%d",i+1];

    //通過字符串反射出對應的類對象
    Class class = NSClassFromString(className);
    //通過類對象創建類的對象
    UIViewController *vc = [[class alloc] init];
    UINavigationController *nvc = [[UINavigationController alloc] initWithRootViewController:vc];
    vc.title = [NSString stringWithFormat:@"界面%d",i+1];
    
    //把4個導航控制器循環依次加入到可變數組中保存起來
    [mArr addObject:nvc];
  

  }

  //把這個數組mArr給標簽控制器所管理
  self.viewControllers = mArr;

//自定義tabBar

[self customTabBar];

}

-(void)customTabBar{

/*********** 1.隱藏系統自帶的tarBar *************/
self.tabBar.hidden = YES;

/*********** 2.根據項目需求添加背景圖片 ************/
UIImageView *bgImageView = [[UIImageView alloc] initWithFrame:CGRectMake(0, screenBounds.size.height-49, screenBounds.size.width, 49)];

// bgImageView.alpha = 0.7;
bgImageView.image = [UIImage imageNamed:@"tabbg"];
bgImageView.userInteractionEnabled = YES;
[self.view addSubview:bgImageView];

/********** 3.根據需求添加多個按鈕或者label **********/
_btnArray = [NSMutableArray array];
CGFloat wSpace = (screenBounds.size.width-120)/5;

for (int i=0; i<4; i++) {
    UIButton *btn = [UIButton buttonWithType: UIButtonTypeCustom];
    btn.frame = CGRectMake(wSpace+i*(30+wSpace), 2, 30, 30);
    //在正常狀態下顯示的背景圖片
    [btn setBackgroundImage:[UIImage imageNamed:[NSString stringWithFormat:@"tab_%d",i]] forState:UIControlStateNormal];
    //在選中狀態下顯示的背景圖片
    [btn setBackgroundImage:[UIImage imageNamed:[NSString stringWithFormat:@"tab_c%d",i]] forState:UIControlStateSelected];
    
    if (i==0) {
        btn.selected = YES;
    }
    
    btn.tag = 100+i;
    //添加點擊事件
    [btn addTarget:self action:@selector(btnClick:) forControlEvents:UIControlEventTouchUpInside];
    [bgImageView addSubview:btn];
    [_btnArray addObject:btn];
}

UILabel *label = [[UILabel alloc] initWithFrame:CGRectMake(wSpace, 34, 30, 2)];
label.backgroundColor = [UIColor yellowColor];
label.tag = 200;
[bgImageView addSubview:label];

}

-(void)btnClick:(UIButton *)btn{
NSLog(@"%ld",btn.tag);

UILabel *label = (UILabel *)[self.view viewWithTag:200];
[UIView animateWithDuration:0.5 animations:^{
    label.frame = CGRectMake(btn.frame.origin.x, 34, 30, 2);
}];


//@[btn1,btn2,btn3,btn4];
for (UIButton *button in _btnArray) {
    if (button.tag == btn.tag) {
        //讓當前點擊的那個按鈕處于選中狀態
        btn.selected = YES;
    }else
    {
        //讓其他的按鈕處于非選中狀態
        button.selected = NO;
    }
}




//**************** 4.根據點擊的button實現頁面的切換 **************************
self.selectedIndex = btn.tag - 100;